Apparatus for working on sheet material

ABSTRACT

An apparatus is disclosed for working on sheet material, such as woven and non-woven fabrics, plastic or paper with a tool which translates over the sheet material to perform a cutting, plotting or other material processing operation. The apparatus holds the sheet material down during the operation and includes a table, such as a vacuum table, which supports the material, either a single sheet or a layup of the material, and a fluid compartment which is positioned over and exposes the material to pressurized air to force the material onto the supporting surface of the table. While maintaining a region of increased air pressure in the immediate vicinity of the tool, the compartment may be translated along one or two orthogonal directions in conjunction with the movements of the tool. The compartment is open or perforated at the side confronting the material to expose the material to the air under pressure within the compartment. When appropriate, a sheet of impervious material may be overlaid on a layup of the material to increase the effective pressure on each ply of the layup.

United States Patent [191 Gerber et al.

[451 Nov. 19, 1974 APPARATUS FOR WORKING ON SHEET MATERIAL [73]Assignee: Gerber Garment Technology, Inc.,

East Hartford, Conn.

22 Filed: June 21,1973

21 Appl. No.2 372,429

Related US. Application Data [63] Continuation-in-part of Ser. No.96,384, Dec. 9,

1970, Pat. No. 3,750,507.

[52] US. Cl 29/559, 83/22, 83/169,

83/374, 83/925 CC, 269/21 [51] Int. Cl D06h 7/00 [58] Field of Search269/21, 20; 83/14, 22,

Primary ExaminerJ. M. Meister Attorney, Agent, or FirmMcCormick,Paulding & Huber [5 7] ABSTRACT An apparatus is disclosed for working onsheet material, such as woven and non-woven fabrics, plastic or paperwith a tool which translates over the sheet material to perform acutting, plotting or other material processing operation. The apparatusholds the sheet material down during the operation and includes a table,such as a vacuum table, which supports the material, either a singlesheet or a layup of the material, and a fluid compartment which ispositioned over and exposes the material to pressurized air to force thematerial onto the supporting surface of the table. While maintaining aregion of increased air pressure in the immediate vicinity of the tool,the compartment I may be translated along one or two orthogonaldirections in conjunction with the movements of the tool. Thecompartment is open or perforated at the side confronting the materialto expose the material to the air under pressure within the compartment.When appropriate, a sheet of impervious material may be overlaid on alayup of the material to increase the effective pressure on each ply ofthe layup.

10 Claims, 13 Drawing Figures PATENIELRGVISISY'! 3,848.32?

sum 1 or 4 PATENTEL, HEY I 91974 SHEET 2 BF 4 PAIENIELHUYIQW 3.848.327

SHEET nor 4 H? H""" .n w W W i I60 ll I l Hi I62 Q76 i llllll \y \I I 52w :5; 54 wt. 5% w ,p:

v l7] l/ l l APPARATUS FOR WORKING ON SHEET MATERIAL CROSS REFERENCE TORELATED APPLICATION This application is a continuation-in-part ofapplicants copending application Ser. No. 96,384, filed Dec. 9, 1970 nowUS. Pat. No. 3,750,507 entitled METHOD AND APPARATUS FOR HOLDING SHEETMATERIAL.

BACKGROUND OF THE INVENTION This invention relates to apparatus forworking on sheet material with a tool while the material is held down ona work table.

In the past, it was cutomary to cut pattern pieces from a layup of sheetmaterial formed by multiple plies of woven or non-woven fabric piled oneupon the other by guiding a motor-driven, reciprocating knife by handthrough the layup. To hold the layup in position during the cuttingoperation, the operator of the knife would use his free hand to pressdown on the layup at a point adjacent to the cutting path traversed bythe knife.

More recent advances in the fabric cutting technology-have brought intouse mechanically guided cutting devices which are numerically controlledby a digital computer to cut pattern pieces from a layup according to aprogram on a punched tape or other memory device. Obviously, it isdangerous and not feasible for an individual to attempt to press a layupof sheet material against a table while the layup is cut by a computercontrolled knife. Other means for pressing the different plies of thelayup together must be employed so that a clean and accurate cut can bemade without lifting or shifting of the fabric during the cuttingprocess and so that a reciprocating knife penetrates a layup of nominalthickness along a substantially vertical path to cut pattern pieces ofsubstantially identical shapes from the upper and lower plies of thelayup. One such apparatus which performs this function by means of avacuum holddown device is disclosed in US. Pat. No.

3,495,492, issued Feb. 17, 1970, and entitIed APPA- RATUS FOR WORKING ONSHEET MATERIAL and having the same assignee as the present invention.

The general aim of the present invention is to provide an improvedapparatus of the aforedescribed type for working on sheet material witha tool while the material is held down on a table.

SUMMARY OF THE INVENTION The present invention resides in an apparatusfor working on sheet material with a tool, for example, a cutting toolwhich traverses the sheet material to cut out pattern pieces forgarments and other articles. The apparatus comprises means such as atable which defines a material supporting surface for suppoing the sheetmaterial in a spread condition and means for producing a region ofincreased fluid pressure above the supporting surface so that the fluidpressure may hold supported sheet material against the surface. Thetable defining the supporting surface may be a vacuum table havingseveral vacuum zones energized when the tool is working over therespective zones. The means for producing the region of increasedpressure includes a fluid compartment which defines a fluid dischargeopening in a portion of the compartment confronting the materialsupporting surface for exposing the sheet material to a fluid underpressure. The fluid compartment generates a region of locally increasedpressure above the sheet material supported on the surface and isprovided with a positioning means to translate with a tool relative tothe sheet material so that the region of increased pressure ismaintained in the immediate vicinity of the tool.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of anumerically controlled cutting apparatus utilizing one cmbodiment of thepresent invention.

FIG. 2 is a sectional view of a portion of the cutting apparatus as seenalong line 22 in' FIG. 1.

FIG. 3 is a fragmentary perspective view showing the detailedconstruction of a fluid compartment utilized in one embodiment of thepresent invention.

FIG. 4 is a fragmentary sectional view of the fluid compartment as seenalong the line 44 in FIG. 3.

FIG. 5 is a fragmentary sectional view of the fluid compartment as seenalong the line 5-5 in FIG. 3.

FIG. 6 is a perspective view of a cutting apparatus utilizing anotherembodiment of the present invention.

FIG. 7 is a sectional view of a portion of the cutting apparatus as seenalong the line 77 in FIG. 6.

FIG. 8 is a perspective view of a cutting apparatus incorporatinganother embodiment of the present invention.

FIG. 9 is an elevated frontal view in section showing the details of thetoroidal fluid compartment of FIG. 8.

FIG. 10 is an elevated frontal view in section showing another toroidalfluid compartment of a type which may be utilized in the cuttingapparatus of FIG. 8.

FIG. 11 is a perspective view of a cutting apparatus incorporating stillanother embodiment of the present invention.

FIG. 12 is a perpsective view of a cutting device cmploying a stillfurther embodiment of the present apparatus with the cutting devicepartially cut away.

FIG. 13 is a fragmentary sectional view of the cutting device as seenalong the lines l3-l3 of FIG. I2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 disclose acutting apparatus which is used to cut pattern pieces from a layupcomposed of sheets of fabric material laid flatwise one upon the other.The cutting apparatus employs a numerically controlled cutting toolwhich is translated over the layup in accordance with commands derivedthrough a computer from punched tape or other memory device. Theapparatus holds the sheet material in a fixed posi tion during thecutting operation and includes a table which defines a work surface forsupporting the material and a pressure producing mechanism for forcingthe material against the work surface of the table.

The cutting apparatus or device, generally designated 10, utilizes acutting tool in the form of a reciprocating knife 12 which is translatedover the layup 14 of sheet material by two numerically controlledcarriages I6 and 18. The carriage I6 straddles the layup and in cludes alongitudinal drive motor (not shown) and two motor driven pinion gears(not shown) which respectively engage two parallel racks and 22 atopposite lateral sides of the layup 14. To translate the knife 12 backand forth over the layup 14 in the longitudinal direction, identified asthe X direction on the layup, commands from a remotely located computerare transmitted through the control cable 24 to the longitudinal drivemotor and the motor drives the pinions engaging the racks 20 and 22 inaccordance with the computer commands.

The carriage 18 supports the knife 12 and is mounted on the carriage 16for translation with respect to the carriage 16 in the lateral directionidentified as the Y direction on the layup 14. The carriage 18 issupported on the carriage 16 of rollers (not shown) which ride on atransverse guide 26 and a transverse frame member 28. A transverse leadscrew 30 mounted to the carriage 16 threadably engages the carriage 18so that rotation of the screw 30 causes the carriage 18 and knife 12suspended from the carriage 18 to be translated back and forth on thecarriage 16 in the Y direction. The combined motions of the carriages l6and 18 along the orthogonal X and Y directions permit the knife 12 to betranslated along irregularly shaped paths through the layup 14 inresponse to the computer commands while cutting the pattern pieces fromthe layup.

A knife orienting motor 32 is mounted at the projecting end of thecarriage 18 opposite the frame member 28 of the carriage 16 and rotatesa platform 34 from which the knife 12 is suspended about a vertical axisnormal to the upper surface of the layup so that the knife remainstangent to the cutting line at the cutting or leading edge of the knife.Another motor (not shown) on the rotating platform 34 causes the knifeto reciprocate along the vertical axis to produce the cutting strokes ofthe knife as it moves through the layup 14. A guide foot 36 is alsosuspended from the rotating platform and rotates with the knife 12. Thefoot 36 is positioned against the upper face of the layup 14 during thecutting operation and prevents the upper plies of the layup from beinglifted during the upward stroke of the knife. The motor 32, platform 34,knife 12 and foot 36 may be suspended from the carriage 18 by means ofan adjustable mount to permit the knife and foot to be adjusted in thevertical direction for layups of different thickness.

The apparatus which holds the layup of sheet material in a fixedposition during the cutting process includes a table 40 on which thelayup 14 is spread and a fluid compartment 42 which is mounted on thecarriage 16 and receives pressurized fluid from a source such as ablower 44 on the carriage 16. Another fluid compartment 46 is includedin the embodiment of the apparatus shown in FIGS. 1 and 2 and cooperateswith compartment 42 in holding the layup 14 on the table 40.

The table 40 is a vacuum table supported in a horizontal position on aplurality of table legs 48 and in cludes an outside casing or frame 50and a bed of material 52 defining the work surface 54 on which the sheetmaterial is positioned flatwise, one sheet on top of the other to formthe multi-ply layup 14. The frame may be utilized as the supportingstructure for the racks 20 and 22 which in turn support the carriages 16and 18 and the knife 12. Various materials may be used to form the bed52, but preferably it comprises an open or closed cell, low-density,foamed, polyethylene plastic material which may be readily penetrated bythe knife 12 during the cutting operation. The reciprocating knife 12 isadjusted to partially penetrate the bed to assure accurate .andefficient cutting of the lower plies in the layup l4.

Ethafoam, a product of Dow Chemical Company. has proven particularlysuitable as a bed material, and such material may be supplied in blocks,as shown, to permit selected portions of the bed which receiveparticularly heavy usage to be replaced from time to time as required.It will be understood that other materials such as bristled mats may beused as the bed material so long as the knife can readily penetrate thematerial and the material provides a sufficiently rigid work surface forsupporting the layup 14 in a fixed position. Of course, in operations onsheet material which do not require that a tool pass through thematerial. for example, a plotting operation, the necessity forapenetrable bed is not present and non-penetrable materials can be employed to define the work surface.

The table 40 is a vacuum table which aids in holding the sheet materialin place by producing a region of reduced ambient pressure orsub-atmospheric pressure at the supporting surface defined by the bed52. A table of this type is illustrated and described in greater detailin US. Pat. No. 3,495,492 issued to the inventors of the presentapplication and having the same assignee. ln one form, the vacuum table40 is constructed to provide a region of reduced pressure at thesupporting surface by drilling passageways 200 vertical through thepenetrable bed material and by constructing a series of plenum or vacuumchambers 202 below the bed 52 in the frame 50 of the table. A vacuumpump 204 is connected through a manifold assembly 206 and valves 208 toeach of the chambers 202. The valves 208 for each of the respectivechambers 202 permit the chambers to be individually evacuated so thatseparate vacuum zones corresponding respectively to the chambers 202 areestablished in the bed 52 of the vacuum table. Each of the valves 208 iscontrolled in synchronism with the movement of carriage 16 supportingthe knife 12 so that the vacuum zone energized will be the zonesupporting sheet material through which the knife is cutting. Two ormore zones may be energized at one time as the knife passes from onezone to another. A more detailed description and explanation of thezoned vacuum table is found in the above-referenced patent.

It will be understood that the bed 52 constructed from bristled mats isideally suited to a vacuum system. For instance, bristled mats areinherently porous or fluid permeable and ambient air can be drawnthrough the bristles to produce a low pressure region at the supportingsurface defined by the free ends of the bristles.

The fluid compartments 42 and 46 as seen in FIGS.

1 and 2 are inverted pans or shells located on opposite sides of theknife 12 and have a shape which is elongated in the Y-direction. Amounting plate connected to one side of the carriage 16 and a similarmounting plate (notvisible) at the other side of carriage 16 have guidesor keys 6], 61 and 63, 63 which mate with corresponding keyways in theconfronting end walls of the compartments. The compartments 42 and 46are adjustably suspended on the guides by means of springs orcounterweights (not shown) connected to carriage 16 so that thecompartments can be shifted in the vertical direction with respect tothe horizontal work surface 54 to accommodate layups of different pliesor thicknesses. Two flexible fluid conduits 62 and 64 are connectedrespectively to the fluid compartments 42 and 46 to deliver the airunder pressure from blower 44 to the interior of the compartments. Eachof the compartments at the side adjacent the layup l4 defines a fluiddischarge opening which exposes the upper face of the layup to thepressure of the air within the compartments. Air seals in the form offlexible elastomeric skirts 66 and 68 are connected, respectively, tothe peripheries of the openings of the compartments and extenddownwardly toward the layup 14 and the table surface 54 to impede theleakage of the air out of the compartments and to generate a cushion ofair at increased pressure above atmospheric pressure under thecompartments, which cushion operates downwardly on the layup.

Adjustment of the biasing force of the springs or counterweights holdingthe compartments 42 and 46 allows the pressure of the air within thecompartment to be varied so that the compartments can be lifted off ofthe layup on the cushion of air. The total force on the affected regionof the layup under the compartment equals the combination of the weightof the compartment plus the biasing and frictional forces. As the airescapes past the skirts 66 and 68, the stream of air assists inspreading the sheet material smoothly on the table 40 and forms a fluidbearing which permits the compartments to translate over the layup 14 onthe cushion of air which supports the compartment and holds the sheetmaterial down on the table 40.

In operation of the cutting apparatus 10, the layup of material is firstpositioned on the surface 54 of table 40 under carriage l6, and blower44 and vacuum pump 204 are started to deliver air under pressure to thecompartments 42 and 46 and to withdraw air from between the layup andthe supporting surface of the table in the zone or zones below theknife. The pressure of the air received within the compartments isapplied to regions of the upper surface of the layup on opposite sidesof and immediately adjacent to the knife 12. The air pressure forces thesheet material compactly against the work table and the vacuum below thesheet material also draws the material toward the table. The cuttingoperation is then begun.

As the knife 12 traverses a cutting path through the layup, the fluidcompartments 42 and 46 move with the component of the knife displacementin the X direction and the knife translates relative to and between thecompartments for components of its displacement in the Y direction. Inthis fashion, the two regions of increased pressure produced by thecompartments move successively over adjacent portions of the layup andremain immediately adjacent the knife regardless of the position of theknife on the layup surface. The valves 208 between the vacuum pump andthe bed 52 are opened and closed by the carriage 16 as the knife 12traverses the vacuum zones controlled by the respective valves.Accordingly, a region of increased pressure above the layup and a regionof decreased pressure below the layup holds the sheet material compactlyin place on the supporting surface and the two regions move insynchronism along the table with the knife.

It will be understood that the pressure of the air received incompartments 42 and 46 is applied to the upper ply of the layup l4 andthe force holding the layup in a fixed position on the table 40 resultsfrom the pressure differential generatedacross the plies of the layup bythe compartments and the vacuum table. In cases where the layup isformed of a fabric material which is air-pervious, the pressuredifferential across the individual plies at the upper portions of thelayup 14 may be greatly reduced due to the filtering of the air throughthe pervious material. Such reduced pressure differentials may not beadequate to hold the upper plies of the fabric material fixedly inposition during the cutting process and, accordingly. it may bedesirable to provide an air-impervious covering over the layup. In suchcase, the upper ply of the layup, as seen for example in FIG. 2, wouldbe an air-impervious covering. With an impervious covering, the forceresulting from the pressure differential between the top and bottomplies of layup I4 is applied across all of the plies of the layup. Suchan impervious covering may be easily provided by a sheet of thin,flexible plastic film. such as a polyethylene sheet. Although the knife12 will cut through the polythylene in the same fashion that it cuts thefabric material, such polyethylene sheets are relatively inexpensive andmay be considered expendable.

In some cutting operations. particularly those in which only one or justa few plies of sheet material are cut, the use of an air-imperviousoverlay may be unwarranted or undesired and the holddown forces may begenerated simply by the air flow through the sheet ma terial between thecompartments and vacuum table. Pressure differentials in the order of lto 10 inches of mercury may be produced across the sheet material byeither the fluid compartments or the vacuum system. The combinedoperation of the compartments and vac uum table makes pressuredifferentials up to 20 inches of mercury possible. The vacuum table andpressurized compartments complement each other by increasing the volumeof fluid flow through the permeable sheet material, and thereby,generating a greater pressure differential. Furthermore. the vacuumtable receives some of the air discharged from the compartments and mayreduce the stream of air escaping from the compartments and flowinghorizontally across the upper surface of the sheet material. The liftingof the upper plies of the material that accompanies such horizontal flowis reduced.

The fragmentary views of FIGS. 3, 4 and 5 disclose an alternateconstruction of the sealing device which may be used on the fluidcompartments 42 and 46 in FIGS. 1 and 2 in place of the flexible,elastomeric skirts 66 and 68. In the alternate construction, the sealingdevice is formed by a porous or apertured member which is located at theperiphery of the opening in the fluid compartment confronting the layup14. In FIG. 3, a corner of a fluid compartment similar to thecompartment 42 is shown with a lateral side wall 70 overhanging the edgeof the layup 14 as would be the case where the layup had a Y dimensionslightly less than the Y dimension of the compartment 42. A porous orapertured member 72 is connected to the inner surface of the lateralside wall 70 at the peripheral edge of the compartment openingconfronting the layup 14. As seen in FIG. 5, the porous member 72 has anL-shaped cross-section and is provided with a series of apertures 74, 74extending through the portion of the member positioned parallel to theupper surface of the layup 14. The member 72 serves as an inwardlyextending seal to prevent air from escaping under the overhanging wall70 of the compartment and the apertures 74, 74 act as pressurestagingorifices which create a staged pressure drop at the edge of the layup.If the wall 70 does not overhang the edge of the layup, the apertures74, 74 allow air within the compartment to be admitted to the regionwithin the member 72 and consequently the pressurized region under thecompartment extends substantially to the wall 70 of the compartmentwithout substantial differences in pressure. 7

Another apertured member 76 is connected to the exterior surface of thecompartment wall 78 joined perpendicularly to the overhanging wall 70.The member 76 has an L-shaped configuration and containspressure-staging orifices or apertures 80 in the portion of the memberextending parallel to the upper surface of the layup. The member 76terminates at a point adjacent the inwardly facing edge of member 72 andis closed at this point by end wall 82. The wall 78 to which the member76'is attached is slightly foreshortened at the bottom edge 84 adjacentthe layup 14 as best seen in FIG. 4. When the compartment is filled withair under pressure, the foreshortened edge 84 allows air to pass readilyunder wall 78, and member 76 with orifices 80 serves as apressure-staging seal to drop the pressure within the chamber graduallyat the periphery of the region of layup 14 experiencing the air,

pressure. The apertures 80 also direct the escaping air vertically awayfrom the layup and thereby reduce the flow of air horizontally under thelower edge 86 of member 76, which flow lifts or shifts the upper pliesof the layup, particularly where the layup has been cut by the knife 12.The member 76, therefore, helps keep the upper plies in a fixed positionduring cutting operatrons.

FIGS. 6 and 7 disclose another embodiment of the apparatus for holdingsheet material in a fixed position while the cutting operation isperformed with the cutting device 10. ln this embodiment of theinvention, the holding apparatus includes the table 40 which has thesame construction as that shown in FIGS. 1 and 2 and a single shell-typefluid compartment 90 which is mounted to the carriage 16 by means of twoguide posts 92 and 94 which are fastened to carriage 16 at therespective ends of the carriage. The compartment 90 can shift verticallyon the posts 92 and 94 for vertical adjustment relative to thehorizontal table similar to the keyway-mounted compartments 42 and 46 ofFIGS. 1 and 2. The compartment 90 envelopes the knife 12, carriage 18,the portion of the carriage 16 along which the carriage 18 translatesand is large enough to envelope the knife and carriage at each pointalong the portion traversed by the carriage 18 so that the compartmentcan be held stationary on carriage 16 while the knife is translated inthe Y direction. Movements of the knife in the X direction caused bymovement of carriage 16 are accompanied by corresponding movement of thecompartment 90 since the mounting of the comrack 22. The blower 96 has adischarging conduit 98' connected to the compartment 90 for dischargingair at low pressure into the compartment. Since the blower 96 is mounteddirectly to the compartment. the conduit 98 can be a rigid rather thana, flexible conduit.

With the layup 14 positioned on the table under the cutting device 10,the blower 96 is started and air pressure within the compartmentgenerates a cushion of air under the compartment which raises thecompartment slightly off of the layup. Biasing springs on posts 92 and94 may be used to adjust the pressure which lifts the comparments offthe layup. Leakage of the air along the interfaces of compartment 90 andthe carriage l6 and posts 92 and 94 can be minimized by providingsliding joints or bellows-type connections which maintain a sealedenvironment within the compartment in spite of relative movements in thevertical direction between the compartment and the carriage and posts.The cushion of air supporting the compartment 90 serves as a fluidbearing permitting the compartment to be translated over the layup inthe X direc-- tion with the carriage 16 and knife 12. Since thecompartment 90 envelopes all of the portion of carriage l6 along whichthe carriage 18 translates. displacements of the knife 12 in the Ydirection are accommodated without moving the comparment.

Although the operation of the compartment 90 is basically the same asthat of compartments 42 and 48 of FIG. 1, it will be understood that theregion of the layup 14 to which the air pressure is applied completelycircumscribes the knife 12 and includes that portion of the layup whichis in direct contact with the knife 12.

FIGS. 8 and 9 disclose another embodiment of the apparatus for holdingsheet material which may be utilized by cutting device 10. The apparatusincludes'a table defining a work surface on which the material issupported and a pressure generating mechanism which circumscribes thecutting tool and translates with the tool over the work surface in eachof the two orthogonal X and Y directions. The table 40 has the sameconstruction as that found in the embodiments of FIGS. 1 and 6,including a bed 52 of penetrable material. However, in addition,penetrable boundary blocks and 112 are positioned on the work surface 54contiguously with the opposite lateral sides of the layup 14. The blocks110 and 112 have a height above the surface 54 which is substantiallyequal to the height or thickness of the layup 14 as seen in FIG. 9 andare formed from the same or similar material as the penetrablebedmaterial 52 so that the cutting tool or knife 12 can be translatedbeyond the edge of the layup into the boundary blocks without damagingthe knife. The mechanism which generates the fluid pressure against thelayup is composed of a stationary source 114 of fluid pressure, a fluidcompartment 116 having a generally toroidal shell configuration and aflexible fluid conduit 118 connecting the stationary source 114 to thecompartment 116. The source 114 may be a large volume air tank or tanksbut is preferably a continuous output blower which is mounted in astationary fashion to an overhead beam or to an other permanent fixtureadjacent the table 40. The source 114 delivers air or other fluid underpressure to the compartment 116 through the flexible conduit 118 whichcan follow movements of the knife 12 over the entire work surface 54 oftable 40. The toroidal comparment 116 circumscribes the knife 12 and issuspended from the carriage 18 by means of two bracket plates 120mounted to opposite lateral sides of carriage 18 so that the compartmentmoves with the knife 12 in both the X and Y directions. The compartment116 may be mounted directly to the platform 34 which supports the knife12 and foot 36 so that the compartment can be adjusted vertically abovethe work surface 54 in conjunction with the adjustment of the knife andfoot for layups of different thicknesses. Relative movement between thestationary source 114 and movable compartment 116 may be readilyaccommodated by the flexible conduit 118 which may be, for example, awire-reinforced plastic hose or similar flexible duct.

FIG. 9 shows a detailed construction of the toroidal compartment 116 inwhich the side of the compartment confronting the layup 14 defines anannular opening that produces an annular region of increased pressurecircumscribing the knife 12. A flexible skirt 122 is mounted to thelower edge of compartment 116 along the inner periphery of the annularopening and another flexible skirt 124 is mounted to the lower portionof compartment along the outer periphery of the annular opening. Both ofthe flexible skirts 122 and 124 extend downwardly toward the layup 14and the work surface 54 and may be constructed of an elastomericmaterial similar to the skirts 66 and 68 in FIG. 2 so that leakage ofthe pressurized air delivered to the compartment is minimized and acushion of air is generated on which the compartment can ride duringtranslation over the layup with the knife. The toroidal compartment 116is shown in FIG. 9 at a position overlying portions of both the block110 and the layup 14 at a lateral edge of the layup. The construction ofthe chamber 116 with the flexible skirt 122 and 124 requires that theblocks 110 and 112 be provided at the edges of the layup withsubstantially the same height as the layup and in contiguousrelationship with the layup so that the knife can work in regionsadjacent the edges of the layup without losing the cushion of air onwhich the compartment translates and without catching the compartment116 or seal 124. on the blocks as the compartment moves over the blocks.Of course a set of blocks having graduated heights might be provided forlayups of different thicknesses.

FIG. discloses another fluid compartment 130 having a toroidal shellconfiguration which may be utilized by the cutting apparatus 10 byconnecting the compartment 130 directly to the carriage 18 in the samemanner that the compartment 116 is connected in FIG. 8. A flexibleconduit 132 is connected to the compartment 130 for supplying air underpressure to the compartment from either a stationary source, such assource 114 in FIG. 8, or a translating source, such as the blower 44 inFIG. 1 or the blower 96 in FIG. 6. The side of the compartment 130confronting the layup 14 is a porous or perforated annulus 134 having aplurality of fine, closely spaced fluid discharge openings or channels136, 136 forming orifices through which the air passes to generate apressure on an annular region circumscribing the cutting tool. Theannulus may be formed as an apertured plate or may be formed from asintered material which allows air to seep through the annulus at alimited rate. The porous annulus eliminates the need for the blocks ofpenetrable material along the edges of the layup 14 since the inherentorificing effect of the channels 136 136 limits the leakage of air outof the compartment 130 when the compartment overhangs the edge of thelayup 14 as shown in FIG. 10.. The operation of the annulus is similarto that of the porous member 72 in FIGS. 3 and 5 except that thecompartment can overhang the edge of the layup by any amount withoutlosing the cushion of air under the portion of the compartment over thelayup since the annulus extends completely over the bottom side of thetoroidal compartment. Even though a small quantity of air may leakthrough the overhanging portion of the compartment. the orificing effectmaintains a pressure within the compartment sufficient to force theregion of layup 14 adjacent the annulus against the work surface 54. Ofcourse. there is no danger of damaging the cutting tool if it shouldexit from the layup during the cutting process since there are noobstacles which could be hit by the tool at the edge of the layup.

FIG. 11 discloses still another embodiment of the apparatus for holdingsheet material under the cutting device 10 which apparatus includes atable defining a work surface and a pressure generating mechanism whichmoves with the cutting tool along the X and Y directions. The table 40which defines the work surface 54 includes the penetrable bed 52 in thesame fashion as that shown in FIG.1. The pressure generating mechanismincludes a stationary source 140 of fluid under pressure, a fluidcompartment 142 in the shape of a cylindrical shell mounted to thecarriage 18 and enveloping the cutting knife 12 and a flexible hose 144serving as the fluid conduit for delivering air under pressure from thesource 140 to the compartment 142. The fluid compartment 142 is mountedto the carriage 18 for adjustment in a vertical direction normal to thesurface 54 and is provided with seals (not shown) at the interfaces withthe carriage 18 to maintain a pressurized envirow ment within thecompartment in spite of the vertical adjustment relative to carriage 18.At the lower portion of the compartment 142 confronting the layup 14, aporous annulus 146 is secured to the internal surface of the compartmentand circumscribes the cutting knife 12 and foot 36. Since thecompartment '142 is mounted to the carriage 18, the compartment moveswith the knife 12 in both the X and Y directions and generates acircular region of increased pressure centered on the knife at the upperface of layup 14. The annulus 146 may have a construction identical tothe annulus 134 in FIG. 10 and operates in essentially the same manneras annulus 134 when the cutting tool 12 overruns the edge of layup 14.To prevent the undue loss of air if the knife 12 translates beyond theedge of the layup, it is advantageous to provide a seal between the foot36 and the inner circular edge of annulus 146. It is also possible thatthe compartment 142 could have an open face confronting the layup and aflexible elastomeric skirt such as skirt 124 in FIG. 10 at the lowerperiphery of compartment 142 in place of annulus 146. Of course, withthe skirt, it is desirable to employ boundary blocks similar to blocks110 and 112 in FIGS. 8 and 9 to allow the knife and compartment tooperate in regions near the edges of the layup.

FIGS. 12 and 13 disclose still another embodiment of the apparatusspecially adapted for holding sheets of air-pervious material against awork surface while the cutting device 10 is operated. The cutting device10 has the same construction as that shown in FIG. 1; however, theportion of the carriage l6 suspended over the table 40 and the carriage18 which supports the knife 12 have been cut away for the sake ofclarity. The construction of the apparatus for producing the region ofincreased pressure in the vicinity of the knife 12 is similar to theapparatus shown in FIGS. 1 and 2 in that two fluid compartments 150 and152 in the form of inverted shells or pans are mounted for verticaladjustment with respect to surface 54 on their respective verticalguides 174 and 176 fixed to support plates 154 and 156 which areconnected in turn directly to the carriage 16 at the opposite lateralsides of the table 40. A blower 158 is carried by the carriage l6 anddelivers air to the compartment 150 and 152 through the flexibleconduits 1M) and 162. In addition to this structure, however, an endlessbelt 164 of an air-impervious material is mounted on two rollers 166 and168 at opposite end faces of the chamber 150. The belt 164 circumscribesthe chamber 150 and has one portion of the belt interposed between thecompartment 150 and the layup 14. The rollers 166 and 168 are mounted invertical slots 170 at each end and, therefore, are allowed to float inthe vertical direction in the same manner as the compartment 150 whichslides on the vertical guides 174. In the same fashion, the compartment152 is circumscribed by an endless belt 180 of air-impervious materialwhich is carried by two rollers 182 and 184 at opposite end faces of thecompartment 152. The rollers 182 and 184 are also mounted in slots 186in the mounting plates 154 and 156 to permit the rollers to floatvertically with the compartment 152 on guides 176. Since the rollers166, 168, 182 and 184 and the compartments 150 and 152 are all mountedto the support plates 154 and 156, the endless belts 164 and 180 aretranslated with the compartments and the knife 12 in the X direction bythe carriage 16.

The fluid compartments 150 and 152 have open sides adjacent the layup 14so that air delivered to the compartments 150 and 152 from blower 158generates a pressure which is applied to the layup 14 through theportions of the impervious belts interposed between the lower, opensides of the compartments and the upper face of the layup. Frictionbetween the belts 164 and 180 and the layup 14 causes the belts torotate as carriage 16 translates the knife 12 in the X direction. Ofcourse, a separate drive arrangement connected to the rollers and beltsand operated synchronously with the drive motors for the carriage 16 canbe provided to insure that the belts do not slide over the upper pliesof the layup 14 and shift the upper plies out of position during thecutting operation. The compartments 150 and 152 remain positionedwithinthe belts 164 and 180 during the translation in the X direction and rideon the cushion of air between the compartments and the belts. The forceof the air pressure on each belt is equal to the weight of thecompartment plus any biasing and frictional forces and is transmittedthrough the belt to a region of the layup adjacent of the knife 12 asthe knife performs its cutting operation. With two regions beingcompressed on opposite sides of the knife, the material under the knifeis also held in place.

Although the apparatus in FIG. 12 which holds the material during thecutting operation operates in basically the same fashion as theapparatus in FIG. 1, that is, the fluid compartments translate with theknife 12 only in the X direction while the knife translates between thecompartments and belts in the Y direction, it is apparent that a layupcomposed of an air-pervious pressure produced by the compartmentsimmediately above the layup is transmitted to every ply within the layupwith full force and effect. Additionally. in the apparatus of FIGS. 12and 13, air escaping from the peripheral edges of the compartments 150and 152 is prevented from streaming over the sheet material and.therefore, cannot lift or blow the sheet material out of position. Theredirection of the fluid flowing from the compartments allows theapparatus in FIG. 12 to be utilized in cases where the fluid generatingthe pressure on the material should not contact the material.

While the present invention has been described in a number of differentembodiments, it should be understood that still further modificationsand substitutions to the method and apparatus disclosed can be hadwithout departing from the spirit of the invention. The specific shapes,sizes and mounting means for the fluid compartments can be variedaccording to the needs of any given operation. The fluids employedto'force the sheet material against the work surface may be varied to becompatible with the particular sheet materials and processes underconsideration. Each of the disclosed fluid compartments can be utilizedin combination with a support table that may or may not have vacuumholddown features. The utility of the invention is not limited to acutting device or process since the invention may be applied withequally satisfactory results to numerically controlled plotters, sewingmachines. drafting equipment, and other devices. Accordingly. thepresent invention while disclosed in a number of specificembodiments-has been described by way of illustration rather thanlimitation.

We claim:

1. Apparatus for holding sheet material comprising: a support tablehaving a bed defining a supporting surface on which the sheet materialcan be spread; vacuum means for producing sub-atmospheric pressure in atleast one region of the supporting surface; and pressurizing meanscooperating with the vacuum means and positioned above the supportingsurface of the table for producing a region of increased pressure aboveatmospheric pressure over sheet material on the supporting surface, thepressurizing means including a fluid compartment positioned over theregion of subatmospheric pressure at the supporting surface and defininga chamber receiving pressurized fluid and having at least one openingconfronting the supporting surface of the table and overlying said oneregion in which the sub-atmospheric pressure is produced whereby thesheet material between the region of sub-atmospheric material can be cutby the apparatus in FIG. 12 without 65 expending a cover sheet ofimpervious material during the cutting process. In both apparatuses,however,

pressure and the fluid compartment is forced tightly against thesupporting surface.

2. Apparatus for holding as defined in claim 1 wherein the support tableis a vacuum table having a porous bed at the supporting surface and thevacuum means for producing the region of sub-atmospheric pressureincludes the table and a vacuum pump connected to the porous bed.

3. Apparatus for holding as defined in claim 2 wherein the vacuum tablehas a porous bed.

4. Apparatus for holding sheet material according to claim 1 furtherincluding a carriage translatable over the support table parallel to thesupporting surface and relative to sheet material on the bed; andwherein the fluid compartment is suspended from the carriage for movingthe region of increased pressure over the sheet material on the bed.

5. Apparatus for holding as defined in claim 4 wherein the support tableis a vacuum table having a bed divided into separate vacuum zones; andthe vacuum means for producing a region of sub-atmospheric pressureincludes the table. a vacuum pump and at least one valve between thepump and each zone in the bed to produce the sub-atmospheric pressure atthe supporting surface in each individual zone of the bed.

6. A method of holding sheet material comprising:

providing a supporting surface on which the sheet material may rest in aspread condition; spreading the sheet material on the supportingsurface; producing a region of increased ambient pressure over a portionof the spread sheet material on the supporting surface;

producing a region of decreased ambient pressure below said portion ofthe sheet material on the supporting surface during the step ofproducing the region of increased ambient pressure; and

jointly moving the regions of increased and decreased ambient pressuresover and below the sheet material cooperatively relative to the sheetmaterial to another portion of the material on the support surfacewhereby selected portions of the material are consecutively exposed toholding forces generated by the cooperative increased and decreasedpressures.

7. A method of holding sheet material as defined in claim 6 wherein thestep of producing a region of increased ambient pressure comprisesplacing a fluid compartment over said portion of the sheet material.pressurizing the interior of the compartment with a pressurized fluidand exposing said region of the sheet material to the pressurized fluidin the compartment.

8. A method of holding sheet material as defined in claim 6 wherein thestep of producing a region of decreased ambient pressure comprisesevacuating ambient air from between said portion of the sheet materialand the supporting surface with a vacuum pump.

9. A method of holding as defined in claim 6 wherein the step ofproviding a supporting surface comprises providing a .porous support beddefining the supporting surface; and the step of producing a region ofdecreased ambient pressure comprises drawing air from between saidportion of sheet material and the supporting surface through the porousbed.

10. Apparatus for holding sheet material as defined in claim 1 wherein:

sealing means circumscribing the opening of the fluid compartment areinterposed between the sheet material on the supporting surface and theopening to impede the leakage of pressurized fluid from the

1. Apparatus for holding sheet material comprising: a support tablehaving a bed defining a supporting surface on which the sheet materialcan be spread; vacuum means for producing subatmospheric pressure in atleast one region of the supporting surface; and pressurizing meanscooperating with the vacuum means and positioned above the supportingsurface of the table for producing a region of increased pressure aboveatmospheric pressure over sheet material on the supporting surface, thepressurizing means including a fluid compartment positioned over theregion of sub-atmospheric pressure at the supporting surface anddefining a chamber receiving pressurized fluid and having at least oneopening confronting the supporting surface of the table and overlyingsaid one region in which the subatmospheric pressure is produced wherebythe sheet material between the region of sub-atmospheric pressure andthe fluid compartment is forced tightly against the supporting surface.2. Apparatus for holding as defined in claim 1 wherein the support tableis a vacuum table having a porous bed at the supporting surface and thevacuum means for producing the region of sub-atmospheric pressureincludes the table and a vacuum pump connected to the porous bed. 3.Apparatus for holding as defined in claim 2 wherein the vacuum table hasa porous bed.
 4. Apparatus for holding sheet material according to claim1 further including a carriage translatable over the support tableparallel to the supporting surface and relative to sheet material on thebed; and wherein the fluid compartment is suspended from the carriagefor moving the region of increased pressure over the sheet material onthe bed.
 5. Apparatus for holding as defined in claim 4 wherein thesupport table is a vacuum table having a bed divided into separatevacuum zones; and the vacuum means for producing a region ofsub-atmospheric pressure includes the table, a vacuum pump and at leastone valve between the pump and each zone in the bed to produce thesub-atmospheric pressure at the supporting surface in each individualzone of the bed.
 6. A method of holding sheet material comprising:providing a supporting surface on which the sheet material may rest in aspread condition; spreading the sheet material on the supportingsurface; producing a region of increased ambient pressure over a portionof the spread sheet material on the supporting surface; producing aregion of decreased ambient pressure below said portion of the sheetmaterial on the supporting surface during the step of producing theregion of increased ambient pressure; and jointly moving the regions ofincreased and decreased ambient pressures over and below the sheetmaterial cooperatively relative to the sheet material to another portionof the material on the support surface whereby selected portions of thematerial are consecutively exposed to holding forces generated by thecooperative increased and decreased pressures.
 7. A method of holdingsheet material as defined in claim 6 wherein the step of producing aregion of increased ambient pressure comprises placing a fluidcompartment over said portion of the sheet material, pressurizing theinterior of the compartment with a pressurized fluid and exposing saidregion of the sheet material to the pressurized fluid in thecompartment.
 8. A method of holding sheet material as defined in claim 6wherein the step of producing a region of decreased ambient pressurecomprises evacuating ambient air from between said portion of the sheetmaterial and the supporting surface with a vacuum pump.
 9. A method ofholding as defined in claim 6 wherein the step of providing a supportingsurface comprises providing a porous support bed defining the supportingsurface; and the step of producing a region of decreased ambientpressure comprises drawing air from between said portion of sheetmaterial and the supporting surface through the porous bed. 10.Apparatus for holding sheet material as defined in claim 1 wherein:sealing means circumscribing the opening of the fluid compartment areinterposed between the sheet material on the supporting surface and theopening to impede the leakage of pressurized fluid from the chamber.